Genetic and environmental factors influenced the birth and weaning weight of lambs

This paper's main goal was to determine the most important factors affecting meat production in the semi-arid region of Ukraine and derive adjustment factors for known non-genetic sources of variation. The study's object was the influence of genetic and non-genetic factors on the birth and weaning weight of lambs. Data from 2,603 ewes were included in the analysis, where 3,961 lambs were obtained during the five years of the research. Their mating evaluated the growth traits of lamb in the Ascanian Fine-Fleece ewes with the sires of the following genotypes, which are the Ascanian Fine-Fleece, the Australian Merino, and the half-bred rams. The influence of the year of lambing, ram genotype, age of dam, type of birth, sex of lamb on the birth, and weaning weight of lamb was also studied. A significant effect on the birth and weaning weight of lambs was established for all genetic and non-genetic factors used in the study (the year of lambing, ram genotype, age of dam, type of birth, and sex of lamb). The interaction year of lambing x ram genotype was significant only for the weaning weight of lambs (P = 0.005), the interaction year of lambing x age of dam was significant only for the birth weight of lambs (P = 0.044), the interaction year of lambing x type of birth was significant both for the birth weight of lambs (P < 0.001), and also for the weaning weight of lambs (P = 0.007). The interaction year of lambing x sex of lamb was significant only for lambs' weaning weight (P = 0.035). In addition to environmental effects, we also noted that the interaction between the ram genotype x type of birth was significant for the weight of lambs both at birth (P < 0.001) and at weaning (P = 0.004). Finally, the significant interaction of three factors (year of lambing x ram genotype x type of birth and ram genotype x age of dam x type of birth) on the birth weight of lamb was also noted. We registered that two-way factor interactions of the year of lambing x age of dam, year of lambing x type of birth, ram genotype x type of birth and three-way factor interactions of the year of lambing x ram genotype x type of birth and age of dam x ram genotype x type of birth had significant effects (P < 0.001...0.044) on birth weight in the Ascanian Fine-Fleece and crossbreed lambs. Effects of the year of lambing x ram genotype, year of lambing x type of birth, year of lambing x sex, and ram genotype x type of birth interaction had significant effects (P < 0.004...0.035) on the weaning weight of lambs.